Electric machine construction



Sept. 27, 1966 F. H. FODOR 3,275,863

ELECTRIC MACHINE CONSTRUCTION I Filed Feb. 1. 1965 4 Sheets-Sheet l Sept. 27, 1966 F. H. FODOR K 3,275,863

ELECTRIC MACHINE CONSTRUCTION Filed Feb. 1. 1965 4 Sheets-Sheet 2 INVENTOR. FZQEA/Z 11 1 5002 ArraewsYS.

Sept. 27, 1966' F. H. FODOR 3,275,863

ELECTRIC MACHINE CONSTRUCTION Filed Feb. 1. 1965 4 Sheets-Sheet 5 flrraewsm:

Sept. 2?, 1966 F. H. FODOR 3,275,863

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United States Patent 3,275,863 ELECTRIC MACHINE CONSTRUCTION Ferenz H. Fodor, Los Angeles, Calif., assignor, by mesne assignments, of fifty-five percent to Elliott M. Norton and forty-five percent to Ferenz H. Fodor and Leslie G.

Turner Filed Feb. 1, 1965, Ser. No. 431,763 12 Claims. (Cl. 310-166) This invention relates in general to electrical machines such as A.C. and DC. motors and generators and alternators, their construction and methods of making the same. More particularly, this invention relates to novel stator and rotor assemblies capable of ready assembly into such machines to provide selectable speed and power output operating characteristics of exceptionally high order. The exemplary embodiments disclosed herein relate to electric motors and alternators of the pancake construction wherein the rotor assemblies include axially spaced notors assembled to a central stator assembly.

This application is a continuation-in-part application of my co-pending United States application for Letters Patent entitled Electric Motor Construction and Method of Making Same, Serial No. 115,685 filed June 8, 1961, now abandoned.

In prior electric motor and generator constructions, particularly in A.C. motors, I have found that the construction employed is complex, expensive and time consuming to manufacture, particularly in the winding of the stator 0r field windings. Further, because of the prior types of construction and methods of making the same, the power output to weight ratings of these electric motors, have been below the value of one. I have devised novel constructions of stator and rotor assemblies, and methods of making electric machines thereof, which overcome these prior deficiencies. The electric machine, in accordance with my invention, is not only easy to manufacture and provides greatly improved results, but is easily modified to obtain diflerent horsepower ratings, r.p.m. ratings and even to change an electric motor into an alternator. For example, an A.C. electric motor, in accordance with my invention, has attained the exceptional horsepower to weight ratio of one. A three-phase, four-pole motor employing my construction and weighing less than five pounds has developed about five horsepower in experimental testing. In addition, the motor construction of the present invention allows the ready change of any given motor from a particular phase construction, such as a three-phase motor, to another, such as a two-phase motor by merely replacing the readily removable stator assemblies. By replacing the rotor assemblies, the same electric motor can be made to operate and function as a highly efiicient alternator.

Generally stated, the machine according to my invention comprises a central ring-like stator having pole faces on the annular sides thereof and a pair of disc-like rotors axially mounted to align with the respective sides of the stator, the rotors being mounted on a rotor shaft passing through the stator and journalled in a pair of bell end housings. According to my invention, the ring-like stator assembly is retained within the machine housing by the clamping action of the bell end housings against each other, when assembled, such that when it is desired to replace the stator, it may readily be removed merely by removing a few bolts holding the bell end housings together and disassembling one rotor from the rotor shaft. The phase and pole characteristics of the motor may be readily changed therefore by merely changing the stator. Further, the motor maybe converted to an alternator by employing a different rotor construction with the same original stator construction.

The stator, in general, includes a plurality of individ'ual segments disposed in a circular array extending transversely of the rotor assembly. Field windings are wound about these segments in a novel manner to provide the number of desired poles and separate levels or tiers for each phase of the motor. The poles for the stator are produced by grouping any desired number of segments together while winding the segments and because of the novel winding method employed in the present invention, produce segments having opposite polarities at the opposite ends thereof. This novel field winding construction doubles the number of poles per turn of winding in the machine and greatly increases its power output characteristics.

The field windings may be of a light weight anodized aluminum tape wound about the segments. Each segment may be comprised of a plurality of iron bars having a shell or coating of plastic resin, as described herein, or may comprise a sintenloy segment of generally triangular cross-section. The stator assembly so constructed may then be centrally disposed about a rotor shaft and a pair of rotors assembled to the shaft.

The rotors may be formed of a rotor blank of magnetic material, such as soft iron, having spaced concentric ring depressions or recesses on one surface and radial slots interconnecting these depressions or recesses. The depressions and slots may then be filled with copper to provide the magnetic paths in the rotors. I have found that the expensive and time consuming step of brazing copper into the depressions and slots may be obviated by producing a good copper bondable surface on the surface of the blank, having the depressions and the slots, by metal spraying liquid molybdenum thereon. The copper may thereafter be applied by metal spraying liquid copper thereon until the recesses and slots are completely filled. The inlay of copper thus provided is securely bonded to the blank and may be very rapidly provided. The blank may also be cleaned by a dry vapor blast prior to the first metal spraying step to remove foreign particles therefrom. Each rotor assembly includes two rotors made as indicated. In an alternative form of rotor construction, a coil of silicon tape may be wound tightly and inserted into a stainless steel cup. This coil may then be slotted and notched to receive a plurality of copper inlays or discs thereon to provide the necessary magnetic paths. In either construction of rot-or, the rotors are easily removable from the stator to allow replacement of either the rotors or the stator.

The rotor and stator assemblies are retained in assembled relationship within a pair of hell end housings. These bell end housings not only provide bearings to support the rotor shaft but also provide means to abut and maintain the central stator assembly in its operative relationship to the rotor assembly.

It is, therefore, an object of my invention to disclose and provide a construction of electric machine having novel stator and rotor assembly construction providing improved operating characteristics wherein the stator and rotor assemblies are readily replaceable to vary the phase and/or pole characteristics of the machine or to change an AC. motor into an alternator.

It is therefore an object of my invention to disclose and provide a construction and method of making same for an easily manufactured dependable polyphase electric motor of the pancake type having exceptionally good horsepower to weight ratio characteristics.

It is another object of my invention to disclose and provide a novel construction of a polyphase electric motor having novel rotor and stator assemblies wherein the number of phases and/or poles of the motor may be readily changed by easy replacement of the stator assembly with another of suitable phase and pole characteristics as desired.

It is a further object of my invention to disclose and provide a construction and method of making of a novel rotor for use in a motor of the character described herein where a magnetic path of copper is easily and readily provided therein in a novel and efficient manner.

It is a still further object of my invention to disclose and provide a stator assembly employing novel stator segments arranged in a novel manner, and a method of making same, wherein a highly efficient motor may be provided through its use.

These and other objects, advantages and resultants of the invention will become readily apparent from the following detailed description of exemplary embodiments of polyphase electric machines, according to my invention, having novel stator and rotor assemblies made according to the method of my invention. Throughout the detailed description of the embodiments disclosed herein, reference will be made to the appended sheets of drawings in which:

FIG. 1 is a transverse section of a polyphase electric motor of the pancake type showing novel stator and rotor assemblies and their arrangement, according to my invention;

FIG. 2 is a side elevation of the stator assembly of FIG. 1 as it would appear at an initial stage of assembly wherein only a single field winding of a first phase portion of the stator has been completed;

FIG. 3 is an enlarged detail view of a portion of the stator assembly of FIGS. 1 and 2 showing a stator segment in perspective;

FIG. 4 is a side elevation of the rotor assembly of FIG. 1 with the rotors shown in cross-section;

FIG. 5 is a front elevation of a rotor blank prior to its finish machining to the shape of the rotor as shown in FIGS. 1 and 4, with only a portion of the slots interconnecting two concentric ring depressions shown;

FIG. 6 is a transverse section of the rotor blank of FIG. 5 taken therein along the plane 6-6;

FIG. 7 is a transverse section of an alternative embodiment of rotor construction for the electric motor of FIGS. 1-5;

FIG. 8 is a partial front elevation of the alternative embodiment of rotor construction of FIG. 7;

FIG. 9 is an enlarged detailed view of an alternative construction of stator segment for the stator of the present invention;

FIG. 10 is a transverse section of an alternative embodiment of rotor construction of the present invention;

FIG. '11 is a partial front elevation of the alternative embodiment of rotor construction of FIG. 10;

FIG. 12 is an enlarged detailed viewof a portion of the rotor assembly of FIG. 10;

FIG. 13 is a transverse section of an alternative embodiment of AC. machine of the present invention;

FIG. 14 is an elevational view of the stator assembly of the machine of FIG. 13; and

FIG. 15 is a section view of the stator assembly of FIG. 14 taken therein along the plane 1515.

An exemplary embodiment of an electrical motor having novel stator and rotor assemblies of the AC. machine according to my invention is shown in FIGS. 1 through 6. As shown in FIG. 1, the motor comprises in general a motor housing indicated generally at 10; a stator assembly, indicated generally at and a rotor assembly indicated generally at 50.

The motor housing, indicated generally at 10', is composed of a rear end bell housing 11 and a front end bell housing 12, which are securely held in assembled relation by the bolts 13 and 14. The opposed abutting surfaces of the front and rear bell housings 11 and 12 are provided with opposed recessed lip receiving recesses 11' and 12, respectively, as shown in FIG. 1. As may be further noted in FIG. 1, the stator, indicated generally 4 at 20, is fixedly held between the front and rear bell housings at a ring lip 21 by the clamping action thereon of the opposed housing surface recesses 11 and 12'. The rotor assembly, indicated generally at 40, is axially mounted on bell housings 11 and 12 by means of the bearings 15 and 16, respectively.

The stator assembly, indicated generally at 20 in FIG. 1, is comprised of a plurality of stator segments 22 and field windings 23. The stator segments 22 are disposed in a circular array, extending transversely of the rotor I assembly. The field windings 23 are wound about the segments 22 on a separate level or tiers for each phase of the motor. The motor shown is a three-phase fourpole motor and the windings 23 are provided on three levels or phases, out of phase with each other. A single quadrant of windings 22, representing a single pole, is shown in FIG. 2. While the exemplary embodiment described herein is a three-phase four-pole motor, it should be understood that any number of phases or poles may be provided as desired.

Stator segments 22, as shown in FIG. 3, are made of a plurality of soft iron bars 24, having a diameter preferabl of .022 plus or minus .007 inches and a length of about 1% inches, compressed together into a wedge-like packet. The segments 22 are made by heating a plurality of soft iron bars, preferably 142 bars of about eight feet lengths, and then forcing them through a suitable die having an opening resembling a truncated triangle. The bars are thereby compressed into a packet having a generally wedge-like cross section. As the heated and compressed bars are fed out of the die, they are coated with a plastic resin to provide electrical insulation thereabout. The packet, being thus formed in an eight :feet length, is then cut into the segments 22, each preferably about 1%. inches long for use in a three-phase stator as shown in FIG. 1, so that they may be readily assembled into the stator assembly.

Another form of stator segment is shown in FIG. 9. Such segment 122 may be constructed of pressed powdered metal shaped to form small. Wedges as shown.

After the segments 22 or 122 have been formed, they are assembled in a circular array, as shown in FIG. 2, with the side surfaces 25 and 26 convergent inwardly toward the center of the array. The segments may be placed on a magnetic chuck having spaced recesses therein to receive the segments to facilitate assembling the stator.

A ported separator 27, made of an insulating material such as fish skin, may be first positioned on the chuck so that the segments 22 are set through ports in the separator when assembled on the chuck. Winding means for inducing magnetic flux in said segments or stator pole pieces are provided as hereinafter explained.

After the segments are arranged in a circular array, as shown in FIG. 2, the field windings 23 for a' first phase are applied. Field windings 23 may be provided of an anodized aluminum tape, preferable .25 inch wide and .003 inch thick having a one mill anodization, which has a large dielectric strength. The tape is first wound about the segment 27, of stator segments 22 as shown in FIG. 2. After several turns have been made about the segment 27, the tape is continued on about the two segments 28 and 29 lying on either side of the segment 27. After several turns have been wound about the segments 28 and 29, forming a coil encompassing the segments 27, 28 and 29, the tape is continued on about the next two adjacent segments 30 and 31 lying outside of the coil formed about the segments 27, 28 and 29. The winding is continued similarly about the segments 32 and 33 and thereafter, similarly on about the segments 34 and 35 completing a single grouping of turns of tape forming a single pole winding, the windings 23 thus provided forming one of the four poles for the firstphase. The tape of windings 23 is then continued on to the next quadrant where a similar but reverse pole winding is made. The direction of winding determines the polarity of the axially spaced end faces or ends of each group of segments, the polarity of such ends or end faces of a group being of opposite polarity.

It is therefore apparent that the field windings may be very rapidly and easily made, particularly so where automatic winding machines are employed. Four pole windings are made in the four quadrants, each resembling that shown in FIG. 2, for each phase, a single continuous tape being employed for all the windings in a particular phase. The windings provided for a single phase are therefore formed of a plurality of individual groupings of turns of the tape, each grouping effecting a stator pole. Each grouping includes a pluraity of turns of tape wound in expanding concentric coils wound about a central axis of the grouping. Each coil includes a plurality of turns and, except for the coil wound about the single segment intersected by the central axis of the grouping, as segment 27, is formed about a pair of segments. The successively expanding coils are formed about successive outwardly spaced pairs of segments (such as the pairs formed by segments 28 and 29, 30 and 31, 32 and 33 and 34 and 35) until a grouping is completed. After the four pole-windings have been wound in the first phase 36, a separator 37 may be placed thereon and a second phase 38 wound upon the segments 22 similar to the first phase 36 but positioned 120 out of phase with it. A third separator 39 may then be placed over the segments 22 and a third phase 40 may be wound thereon 120 out of phase with the second phase 38. Any number of phases may thus be provided. Similarly, any number of poles may be provided by varying the number of pole windings wound.

After completing the windings 23, a shaft housing ring 41, preferably made of stainless steel, is placed in the center of the stator assembly as shown in FIG. 1, and a stator housing ring 42 is assembled about the segments 22 and windings 23 and spot welded, preferably in eight places as shown in FIG. 2, together about the ring lip 21.

The assembled stator may then be dipped in an insulating varnish and baked after removal therefrom for about eight hours at about 275 F. This step may then be repeated to insure that a good coating of varnish is applied to the stator assembly. Thereafter, the stator is spotted with a plastic resin and baked for about eight hours at about 250 F. to provide a permanent insulation to the stator. The stator assembly is then finish machined to the finished assembly of FIG. 1 by boring out the shaft housing ring 41 to a finished size and grinding the surfaces of segments 22 to clean off any varnish and plastic resin adhering thereto, exposing the soft iron bars 24 of the segments.

The stator assembly is readily inserted and removed from the motor housing, being held therein by the clamping action of the front and rear bell housing 11 and 12, respectively, upon the ring lip 21. Therefore, the motor, according to my invention, may be readily changed from a three-phase four-pole motor to a two-phase two-pole motor, for example, by merely changing the stator assembly for another suitably wound stator.

Referring now to FIGS. 4, 5 and 6, the exemplary rotor assembly comprises a pair of opposed rotors 51 and 52, made of a magnetic conductive material according to my invention, and a rotor shaft 53. Each rotor is provided with generally flat parallel front and rear surfaces, the front surface having two spaced concentric generally circular depressions or recesses 54 and 55. The depressions 54 and 55 are interconnected by radial grooves 56, as shown in FIG. 5. These grooves and depressions are filled with copper to provide magnetic paths in the rotors. The rotors 51 .and 52 are held upon the rotor shaft 53', comprising a rotor assembly, by bolt fasteners 57 threaded into flange portions 58 and 59 which are integral with the rotor shaft 53.

The rotors 51 and 52, according to my invention, are made by first forming a rotor blank 60, as shown in FIG. 6, with two concentric circular depressions 54 .and

. 55 in one surface interconnected by a plurality of equally spaced radial grooves 56. The circular depressions and grooves may be provided in the rotor blank by known machining operations or the blank can be initially cast with the depressions and grooves therein. The blank 60 is further provided with a center shaft receiving opening 61 and a pair of mounting fastener receiving counter bored holes 62 and 63. The blank 60, thus provided, is then preferably blasted with a super heated, dry vapor to thoroughly clean any foreign matter off it. Thereafter, the front surface of the blank is selectively treated to provide the surfaces of the depressions and grooves with a surface readily bondable to copper. Preferably, a thin coating of molybdenum is sprayed on the blank surface 64, having the depression and slots therein, to provide a bondable surface for metal spraying copper thereon. The molybdenum may be sprayed on the blank 60 in liquid form by generally known means. After the molybdenum coating has set, the depressions and slots are virtually filled with copper, preferably by metal spraying liquid copper by generally known means on the blank 60 until the depressions 54 and 55 and slots 56 are filled.

Blank surface 54 may then be finish machined, after the inlay of copper is set, to provide a smooth, flat, uniform surface. The back side 65 of the blank 60 may then be finish machined to provide the finished rotor of FIG. 4. Material may be cut drilled or otherwise removed from the back side 65, as required, to properly balance the rotors after the copper is sprayed into the ring depressions 54 and 55 and radial slots 56.

An alternative embodiment of rotor construction is shown in FIGS. 7 .and 8. This alternative exemplary embodiment includes a toroid coil of silicon tape preferably .004 inch thick and .5 inch wide, wound very tightly and inserted into a non-magnetic material cup 151, preferably made of stainless steel. The coil 150 is then slotted to provide a plurality of radial slots 156, prefer- ,ably about one-eighth inch wide and about forty-six in number. Notches or recesses 154 and 155 as shown are also turned into the coil 150 by any suitable machining operation to provide recesses and slots as in the rotor blank of FIGS. 4-6. A plurality of stamped copper discs 157 are provided with cutout portions corresponding to the raised wedge-like bars or segments 158 on the toroid coil 150 formed by the recesses 154 and 155 and the radial slots 156. A plurality of such discs 157, preferably five discs of about one-thirty-second of an inch thickness, are pressed over the bars 158 onto each rotor assembly. A second stainless steel cap 159 may be used to hold the assembly of coil and discs together, fastener 160 holding caps 151 and 159 thereto. A central bore 161 is provided for assembly of the rotor to a rotor assembly of axially spaced rotors on a central rotor shaft.

The rotors 51 and 52 of FIGS. 5 and 6 or the embodiment of FIGS. 7 and 8 may then be assembled on the shaft 53 with the stator assembly, indicated generally at 20, positioned therebetween. With the further assembling of the bell end housings 11 and 12 about the rotor assembly and stator assembly, and suitable wiring connections made, the motor is complete.

The motor is, therefore, readily assembled or disassembled, to replace the stator for instance, by merely turning a few bolts and removing the bell end housings. The stator, by the use of the segments 22 and 122 and the winding method of the present invention is readily and quickly assembled. The rotors, according to my invention, are also readily made, the copper for the magnetic paths therein being applied by metal spraying rather than by the more difiicult previously employed brazing operation or by press fitting copper discs to the rotor base.

Most importantly, the motor construction disclosed herein has provided polyphase electric motors of the character described which produce more horsepower per pound than a ratio of one to one, obtaining more than one horsepower for each pound of weight. The importance of such HP. to weight ratio cannot be underestimated, particularly when the use of electric motors in space technology, for an example, is considered.

I have found that the operation of the electric motor of the present invention produces predictable speeds from stators having different numbers of poles, for example with 120 volt 400 cycle current:

Number of Poles in Stator: Rpm. 2 24,000 4 12,000

and with 120 volt 60 cycle current:

Number of Poles in Stator: R.p.m. 2 ,600

By merely removing the bolts '13 and 14 and removing a bell end housing and one of the rotors, the stator can be readily replaced to provide any r.p.m. value for the motor desired in view of the current supplied. Further, I have found that the stator construction of the present invention operates as effectively in an alternator as it does in a motor and that by replacing the rotors and housing, the motor of the embodiments of FIGS. 1 through 9 becomes a highly efiicient alternator.

Referring now to FIGS. 10 through 15, another exemplary embodiment of AC. machine according to the present invention will be described. The stator, indicated generally at 120, includes a plurality of segments 122 disposed in a circular array, as best seen in FIG. 14. The field windings are wound around groups of segments, as in the prior exemplary embodiment, to provide however many or few poles as desired, from two to thirty-six or more. As shown in FIG. 14, the exemplary embodiment includes three segments wound in each group, as segments 127, 128 and 129, providing twelve poles. The windings are wound in opposite directions around adjacent groups of segments to give opposite polarity to adjacent poles. It is important to note that the method of winding employed in accordance with the present invention produces opposite polarities at the opposite ends or faces of each segment 122 in each group.

The identical stator assembly, indicated at 20 in FIGS. 1 and 2 may be employed in the exemplary embodiment of FIGS. 13 through 15. The exemplary stator assembly indicated at 120 in FIGS. 13 through 15 differs from that of FIGS. 1 through 3 herein in the provision of sinterloy stator segments 122 in place of segments 22. However, a different rotor construction is employed to make the machine operate as an alternator and a slightly larger bell housing is employed including bell ends 111 and 112 fastened together by bolts 113 and :114. The housing may be made to receive any of the rotor assemblies shown. Bell ends 111 and 112 removably clamp the flanges 21 of the stator assembly 120 between recesses 111' and 112' as in the prior embodiment and also similarly include bearings 115 and 116 to receive and rotatably mount the rotor assembly central axis or shaft 153.

The exemplary embodiment of a rotor assembly which may be employed with the previously disclosed stator assembly to provide an alternator machine, in accordance with the present invention, is shown in FIGS. 10, 11, 12 and 13. Such rotor assembly is indicated generally at 250 and includes a pair of opposed rotors 251 and 252.

Each rotor, as best seen in FIGS. 10 and 11 comprises a rotor base 260 having a central bore 261 to receive shaft 1153 and an enclosing cover 262. The rotor base and cover are made of non-magnetic material, preferably stainless steel. A plurality of stainless steel cap screws 26 3 are employed to mount each rotor to flanges 258 and 259 on the rotor shaft 153. The rotor base 260 is also pro vided with a circular recess 254 about a central hub portion to receive a plurality of rotor pole pieces indicated generally at 270.

Each rotor pole piece, indicated generally at 270 and shown in detail in FIG. 12, includes a pair of generally wedge shaped parts 271 and 272 made of magnetic material.

Each of the pole piece parts 271 and 272 preferably are made of powdered metal pressed and shaped to the forms illustrated. The chemical composition of these rotor pole pieces, as may the form of stator segment 122 shown in FIG. 9, is preferably comprised of iron (Fe) particles with addition thereto of (in percentages):

Si1.80-2.20 (to be kept below 4%) Rotor pole piece part 271 includes a body portion 273 and a projecting portion 275. Part 272 includes a body portion 274 and an integral arbor portion 276 extending outwardly thereof as shown in FIG. 12. Arbor portion 276 is provided at its outer end with a truncated triangle shaped cavity 277 to receive the similarly shaped projection 275 of the other part 271. Parts 271 and 272 may therefore be assembled to each other to provide a pole piece with a central arbor portion 276 adapted to receive a rotor coil 280. Coil 280 is preferably made of aluminum tape, as in the field windings of the previously described stator assembly, placed about the arbor portion 276 of the pole piece part 272 prior to the assembly of the two parts 271 and 272 together. With the coil 280 on the arbor portion 276, the parts 271 and 272 may be easily fitted together with projection portion 275 received within cavity 277 and assembled to the rotor base 260 within slots 255 by the provision of a plurality of ferris cap screws 271, as shown in FIGS. 10 and 11. Each of the parts 271 and 272 is provided with a central bore 279 and 278, respectively, to receive the cap screws 281.

The truncated triangle or wedge cross-sectional shapes of the pole piece parts are designed to easily fit into the rotor base recesses 254 and to provide uniform spacing therebetween when a plurality of such pole pieces are assembled to the rotor base 260, as seen in FIG. 1'1. Also, each of the coils 280 is insulated by insulation material 282 from its associated pole piece and suitable wiring is provided for interconnecting these rotor windings or coils 180. The steel cover 262 is assembled to the rotor base, after all the pole pieces have been put in place, by spot welding cover plate 262' onto the can. shape portion. Each rotor assembly may then be assembled to the main shaft 153 in the machine of FIG. 13 by the aforementioned cap screws or fasteners 263 which 'fasten the rotor assembly to flanges 258 and 259 on the main shaft.

It may be seen from the foregoing description of an exemplary embodiment of an alternator machine in accordance with the present invention, that the stator assemblyof the present invention may be employed in various AJC. machines with rotor assemblies of varying construction. The ease of assembly Oif the stator portion to the machine bell housings and the ready interchangeability of the stator with different rotor assemblies provides uniq-ue adaptability of the present invention to varying demands of an A.C. machine user. For example, the specifications of the exemplary A.C. machine of FIGS. through are: voltage, 12 A.C.; cycle, 60; phase, 3; pole, 12; and amps., 80. It has been found that the performance of this exemplary machine produces an output of 960 watts (max) at 750 rpm. These specifications may be changed as required by merely replacing the stator. The alternator may even be changed to a D0. generator by substituting a single phase stator and the addition of conventional commutator means.

The foregoing description of electric machines, in accordance with the present invention, are exemplary embodiments only and it should be understood that other modifications, alterations and ramifications of the construction and methods of making same may be made within the scope of my invention, which is defined by and limited only by the following claims.

I claim:

1. In an electric machine of the type having a central stator assembly and a pair of axially spaced rotors, one mounted at each side of the stator assembly in close rotatable relation, the provision of a stator assembly comprising:

a plurality of magnetic segments disposed in a generally circular array with axes thereof parallel and lying transversely of the array and including axially spaced opposite end faces; and

means for inducing magnetic flux in said segment including a plurality of windings of non-magnetic material wound about said segments in directions perpendicular to said axes to provide opposite end faces of each segment with opposite polarities, said windings being wound about groups of segments of one or more to provide selectable numbers of stator poles wherein the windings of adjacent groups are wound in opposite directions to provide opposite polarities to adjacent poles.

2. The provision of stator assembly as in claim 1 wherein each group of segments includes three segments or more with a central axis of the group passing through :a center segment of the group and said windings comprise a continuous winding of electrically conductive metal tape wound in each said group in expanding concentric coils wound about and out from a center axis of said group, each coil including a plurality of turns of said tape wound first about a single segment intersected by said central axis and thereafter wound in expanding concentric relationship about successive pairs of segments spaced on each side and outwardly from said single segment of said group.

3. A highly efficient electric machine having a removable stator assembly adapted for use as an electric motor or generator whose phase and/or pole characteristics may be changed readily by replacing the stator assembly, said machine comprising:

a pair of opposed separable bell end housings to receive and enclose a stator assembly and a rotor assembly, each said housing including journal bearing means to rotatably mount a rotor shaft transversely of the housing and said housings having abutting surfaces upon assembly to each other;

holding means for releaseably holding said bell end housings together in abutting assembled relation;

a rotor shaft traversing the interior of said housings and rotatably mounted therein by said journal hearing means;

a pair of axially spaced rotors mounted on said rotor shaft and including magnetic circuit path means on inner opposed surfaces thereof;

a stator assembly comprising a plurality of magnetic segments dipsosed in a generally circular planar array with axes thereof lying transversely of the array and including axially spaced opposite end faces and a plurality of windings of non-magnetic material wound about said segments in directions perpendicular to said axes to provide opposite end faces of each segment with opposite polarities, said windings being wound about groups of segments of one or more to provide selectable numbers of stator poles and in selectable numbers of phases wherein the windings of adjacent groups are wound in opposite directions to provide opposite polarities to adjacent poles;

a shaft housing ring provided at the approximate center of the array of wound groups of segments to freely receive said rotor shaft therethrough;

a stator housing ring enclosing outer marginal areas of said array and including an outwardly extending periferal ring lip; and

clamping means on said opposed bell end housings to releaseably clamp said stator assembly by said ring lip within said housing in assembled relation to said rotor assembly with said rotor shaft passing freely through said stator housing ring and said axially spaced opposite end faces of said stator segments in close spaced relation to said rotor magnetic circuit path means,

said stator assembly being readily removable from said clamping mean-s and bell end housings upon release of said holding means and removal of one of said bell ends and one of said rotors from said rotor shaft to allow ready replacement of said stator assembly by a similar stator assembly or one of different phase and/or pole number characteristics.

4. The electric machine of claim 3 wherein each of said rotors comprises:

a coil of non-magnetic tape tightly wound and inserted into a non-magnetic cup, said coil being provided with a pair of concentric spaced recesses interconnected by .a plurality of radial slots to provide a pluirality of upstanding spaced wedge shaped bars; an

a plurality of magnetic material discs provided with cutout portions corresponding to the shape of said bars pressed into said recesses and slots to provide the magnetic path of the rotor.

5. The electric machine of claim 3 wherein each of said rotors comprises:

a rotor base of non-magnetic material having a central bore to receive said rotor shaft through a central hub portion and an outwardly spaced concentric recess to receive rotor pole pieces;

a plurality of rotor pole pieces of magnetic material disposed in and spaced apart in said recess; and

a rotor coil of magnetic conductive material wound about each said rotor pole piece and magnetically insulated from said rotor base;

said machine being thereby adapted to be used as an alternator.

6. The electric machine of claim 5 wherein each said rotor pole piece comprises a pair of pressed powdered metal parts assembled together providing a central arbor portion of reduced cross-sectional area and said rotor coils comprise a plurality of turns of aluminum tape assembled to said arbor portion, said :parts and coil being held in assembled relation within a slot formed in a wall of said rotor recess by non-magnetic faster means.

7. A highly efficient electric machine comprising:

a motor housing rotatably mounting a rotor shaft traversing the interior of said housing;

a pair of axially spaced rotors mounted on said rotor shaft includin-g magnetic circuit path means on inwardly facing opposed surface; and

a stator assembly comprising a plurality of magnetic,

segments disposed in a generally circulary array with axes thereof parallel and lying transversely of the array and having axially spaced opposite end faces opposing and closely spaced to said rotor inwardly facing surfaces; and

a plurality of windings of non-magnetic material wound about said segments in directions perpendicular to said axes to provide said opposite end faces of each segment with opposite polarities, said windings being wound about one or more segments in groups to provide selectable numbers of stator poles with the windings of adjacent groups wound in opposite directions to provide opposite polarities to adjacent poles, said windings being provided in a plurality of adjacent tiers of separate windings wherein the groups in each tier of windings are positioned out of phase with the groups in an adjacent tier.

8. The electric machine of claim 7 wherein each of said rotors comprises:

a coil of non-magnetic tape tightly wound and inserted into a non-magnetic cup, said coil being provided with a pair of concentric spaced recesses interconnected by a plurality of radial slots to provide a plurality of upstanding spaced wedge shaped bars; and

a plurality of magnetic material discs provided with cutout portions corresponding to the shape of said bars pressed into said recesses and slots to provide the magnetic path of the rotor.

9. The electric machine of claim 7 wherein each of said rotors comprises:

a rotor base of non-magnetic material having a central bore to receive said rotor shaft through a central hub portion and an outwardly spaced concentric recess to receive rotor pole pieces;

a plurality of rotor pole pieces of magnetic material disposed in and spaced apart in said recess; and

a rotor coil of magnetic conductive material wound about each said rotor pole piece and magnetically insulated from said rotor base;

said machine being thereby adapted to be used as an alternator.

10. In an electric machine of the type having a central stator assembly and a pair of axially spaced rotors, one mounted at each side of the stator assembly in close rotatable relation, the provision of a stator assembly comprising:

a plurality of magnetic segments disposed in a generally circular array with axes thereof parallel and lying transversely of the array and including axially spaced opposite end faces; and

means for inducing magnetic flux in said segments including a plurality of tiers of separate windings of non-magnetic material wound about said segments in directions perpendicular to said axes, said windings in each tier being continuously wound about groups of segments of one or more to provide selectable numbers of stator poles wherein the windings of adjacent 'groups'are wound in opposite directions to provide opposite polarities to adjacent poles, said windings in adjacent tiers being positioned degrees out of phase to each other.

11. In an electric machine of the type having a central stator assembly and a pair of axially spaced rotors, one mounted at each side of the stator assembly in close rotatable relation, the provision of a rotor assembly comprising:

a coil of non-magnetic tape tightly wound and inserted into a non-magnetic cup, said coil being provided with a pair of concentric spaced recesses interconnected by a plurality of radial slots to provide a plurality of upstanding spaced wedge-shaped bars; and

a plurality of magnetic material discs provided with cut-out portions corresponding to the shape of sad bars pressed into said recesses and slots to provide a magnetic path of the rotor.

12. In an electric machine of the type having a central stator assembly and a pair of axially spaced rotors mounted on a rotor shaft extending through the stator, one rotor mounted at each side of the stator assembly in close rotatable relation, the provision of a rotor assembly comprising:

a rotor base of non-magnetic material having a central bore to receive the rotor shaft through a central hub portion and an outwardly spaced concentric recess to receive rotor pole pieces;

a plurality of rotor pole pieces of magnetic material disposed in and spaced apart in said recesses, each said rotor pole piece including a pair of pressed powdered metal parts assembled together providing a central arbor portion of reduced cross-sectional area; and

a rotor coil of magnetic conductive material wound about each said rotor pole piece and magnetically insulated from said rotor base, each said rotor coil including a plurality of turns of aluminum tape assembled to the arbor portion of the associated rotor pole piece.

References Cited by the Examiner UNITED STATES PATENTS 1,196,618 4/1914 Turbayne 310- X 2,550,571 4/1951 Litman 310-268 X 2,683,232 7/1954 Weissheimer 310-268 2,711,008 6/1955 Smith 29-1555 2,718,049 9/1955 Prache 29-15561 2,880,335 3/1959 Dexter 310-268 X 2,897,387 7/1959 Welter 310-268 2,935,785 5/1960 Stein 29-1555 2,964,587 12/1960 Minot 161-113 X 3,023,330 2/1962 Roters 310-268 3,041,486 6/1962 Mofiitt 310-168 3,048,723 8/1962 Watson 310-268 X 3,132,272 5/1964 Macfarlane 310-168 ORIS L. RADER, Primary Examiner. G. SIMMONS, Assistant Examiner 

1. IN AN ELECTRIC MACHINE OF THE TYPE HAVING A CENTRAL STATOR ASSEMBLY AND A PAIR OF AXIALLY SPACED ROTORS, ONE MOUNTED AT EACH SIDE OF THE STATOR ASSEMBLY IN CLOSED ROTATABLE RELATION, THE PROVISION OF A STATOR ASSEMBLY COMPRISING: A PLURALITY OF MAGNETIC SEGMENTS DISPOSED IN A GENERALLY CIRCULAR ARRAY WITH AXES THEREOF PARALLEL AND LYING TRANSVERSELY OF THE ARRY AND INCLUDING AXIALLY SPACED OPPOSITE END FACES; AND MEANS FOR INDUCING MAGNETIC FLUX IN SAID SEGMENTS INCLUDING A PLURALITY OF WINDINGS OF NON-MAGNETIC MATERIAL WOUND ABOUT SAID SEGMENTS IN DIRECTIONS 